constify security_path_truncate()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/security/security.c b/security/security.c
index 3644b034..23ffb6c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -478,7 +478,7 @@
 }
 EXPORT_SYMBOL(security_path_rename);
 
-int security_path_truncate(struct path *path)
+int security_path_truncate(const struct path *path)
 {
 	if (unlikely(IS_PRIVATE(d_backing_inode(path->dentry))))
 		return 0;